SCR Catalyst Reductant Dosage Control via Axial Simulation
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Solution Overview
Problem
Current SCR catalyst dosage control methods do not accurately account for local ammonia storage distribution across the catalyst, leading to inefficiencies and ammonia slip issues, especially during temperature changes and dynamic operating conditions.
Innovation Solution
A method involving simulation of reductant dosage based on expected temperature profiles across axial sections of the catalyst, with adjustments made through interpolation between fill-level maintaining and maximum dosages to optimize reductant injection, ensuring real-time control and minimizing ammonia slip.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If closed-loop control of total NH3 fill level is used, then dosage accuracy is improved, but local distribution of ammonia storage across the catalyst is not accounted for leading to ammonia slip
Solution Approach 1:
The catalyst is divided into multiple axial sections (e.g., first, second, and third sections) along the exhaust flow direction. Each section has its own ammonia storage amount calculation and dosage adjustment, allowing local distribution control instead of uniform total fill level control. This segmentation enables precise dosing that prevents ammonia slip while maintaining overall dosage accuracy.
Solution Approach 2:
Different axial sections of the catalyst are treated with different dosage strategies based on their local conditions. The control unit calculates required dosage adjustments for each section individually based on temperature profiles and ammonia storage amounts specific to that section, rather than applying a uniform control approach across the entire catalyst.
2Productivity
If temperature-dependent target fill level control is applied, then catalyst efficiency is improved, but during temperature changes (e.g., acceleration) dosage pauses occur reducing productivity
Solution Approach 1:
The control unit predicts future ammonia storage amounts in each axial section based on current temperature profiles and exhaust conditions. By anticipating how ammonia storage will change during temperature transitions, the system proactively adjusts dosage to maintain optimal levels without pausing, preventing both over-dosing and under-dosing during dynamic operating conditions.
Solution Approach 2:
The dosage control system dynamically adapts to changing temperature conditions by continuously updating temperature profiles for each axial section and adjusting dosage requirements in real-time. This dynamic approach allows the system to maintain optimal ammonia storage levels during acceleration and deceleration without the dosage pauses that occur in static temperature-dependent control systems.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for precise adjustment of reductant dosage, maximizing NOx conversion while keeping ammonia slip below defined limits, even under varying temperature conditions, by simulating and interpolating between different dosage scenarios in real-time.
Implementation Method 1
catalysts based on the principle of selective catalytic reduction (SCR) are used, in which the nitrogen oxides (NO, NO2, collectively NOx) are converted by means of ammonia to nitrogen (N2) and water
Implementation Method 2
an aqueous urea solution is injected into the exhaust gas, which in turn gives rise to carbon dioxide CO2 and ammonia NH3 at suitable temperatures
Implementation Method 3
SCR catalysts known nowadays store ammonia/NH3 by adsorption on the catalyst surface
Data Source
AI summary
A method of adjusting the dosage of a reductant for an SCR catalyst, comprising: determining (110) an expected temperature profile in at least one axial section of the catalyst (70) for a defined period of time (tSim); firstly simulating (120) the resulting amount of reductant beyond the at least one section of the catalyst with a first defined dosage of the reductant depending on the expected temperature profile determined; comparing the first simulated amount of reductant with a limit; depending on the result of the comparison, choosing a second defined dosage and secondly simulating (130, 160) a resulting amount of reductant beyond the at least one section of the catalyst (70) with the second dosage; comparing the second simulated amount of reductant with the limit; and adjusting (140, 150, 170, 180, 190, 195) the dosage for injection of the reductant into the catalyst based on the first and/or second comparison.